a. Field of Invention
This invention pertains to a papermaking machine for making a continuous paper sheet from a wet paper web, and more particularly to a web conditioning assembly used for removing water and conditioning a felt used in said machine, said assembly including a suction chamber which is rotatable for easy cleaning or disassembly.
b. Description of the Prior Art
In papermaking or Fourdrinier machines, various means are used for removing water from a continuous wet paper web to obtain a paper sheet having a preselected water content, density, and other characteristics. For example, the wet paper web is contacted with a continuous felt and then the felt and the paper web are passed through a press nip and/or other means for removing water from the paper web and transferring it to the felt. After the web and felt are separated, the felt traverses one or more devices used for dewatering and conditioning the felt. Devices are known in the art, such as felt suction pipes or uhle boxes, which consist of an elongated pipe extending across the width of the felt. The pipe has a longitudinal, relatively narrow slot, usually defined by a cover secured to the pipe. At least one end of the pipe is in communication with a source of vacuum to produce suction through the slot, thereby extracting water from the felt. A lube shower may be mounted upstream of the pipe slot for wetting the felt before it traverses the slot for conditioning the felt. After a prolonged use, the felt may pick up foreign materials, including small segments of the paper web. These foreign materials are removed from the felt by the suction pipe, and may get lodged into the slot of the pipe requiring cleaning.
Economically it is more convenient to keep the machine line running without cleaning and reconditioning the felt for the short time period required to clean the suction slots. While this procedure may result in some of the paper sheet being discarded because it does not meet certain specifications, it is still cheaper in the long run then stopping the line altogether because the expensive and time consuming restarting of the machine is avoided. Various types of support arrangements were used in prior art papermaking machines to rotate suction pipes for cleaning. However, previous attempts for rotating the pipes were uneconomical because they used bearings which surround the pipe. Because of their size these bearings were expensive and it was hard to keep them sealed against the wet and hostile environment. Moreover, because of the size of the pipes and the bearings a large torque was required to turn the pipes.